The present invention relates to an apparatus and method of bending a vehicle's axle and especially to a method and apparatus for bending a vehicle's solid or non-steering axle, such as the solid rear axle of a vehicle or a solid axle of a semi-trailer, to align the toe angle of the wheels mounted to the solid axle.
Properly aligned wheels of a vehicle have long been a necessity for long tire life, handling ease and for achieving optimal fuel economy. The vehicle wheels need to travel in a straight line, with all wheels pointing in the same direction. That is, all four wheels must be square to each other and square to the road surface. All four wheels need to be parallel to one another and the axles perpendicular to a common center line.
Full attention has generally focused on the alignment of the front wheels. However, a misaligned solid rear axle housing and axle, or the solid axle housing on a semi-trailer, can also result in reduced tire life and reduced fuel economy. A misaligned axle causes excessive tire drag and creates undesirable lateral forces. Even in new trucks, studies have shown that most solid axles need alignment to align the solid axle housing and axles relative to the suspension element and frame of the vehicle and to adjust the toe angle of the wheels mounted on the axle. The vehicle wheels need to be parallel to one another. Because of the increased tire wear and reduced fuel economy, even small mis-alignments of a fixed axle become particularly important for freight carrying vehicles that must travel long distances. However, obtaining the proper alignment in an assembly line setting is difficult as is the minute adjustment that must be made quickly and accurately.
It has been common to perform a front end alignment using laser based wheel alignment systems. The axis about which the front wheel of an automobile or truck turns as it travels down the road must be carefully set to minimize tire wear, for safety and for stable handling characteristics. The orientation of these axes is determined by three angles. The toe angle specifies the angle between the rim of the wheels and a line drawn parallel to the direction in which the vehicle is pointed while the camber angle specifies the angle between the rim of the wheels and vertical while the caster angle specifies the angle between the vertical and the axes about which individual wheels turn when changing direction. These angles are specified individually for each wheel for each model and make of a vehicle. It must be periodically tested and reset to ensure continued economic and safe vehicle performance. However, in addition to front wheel alignment, it is desirable to set the toe angle of a solid rear axle or semi-truck trailer solid axles to avoid wheel scrub or dog tracking and reduced tire wear and reduced mileage for the vehicle.
The present invention is directed to correcting the toe angle of wheels mounted to a solid rear or trailer axle housing to reduce scrub in the axle wheels. The wheel angle being only slightly out of alignment will produce increased tire wear and reduced mileage for a vehicle. A laser alignment system is used for aligning both the front end and the wheels mounted to an axle having a solid axle housing in which a laser is attached to each vehicle wheel spindle or hub, as set forth in the Loescher U.S. Pat. No. 6,823,598. The lasers are pointed at targets to measure and bring the wheels into proper alignment.